Autocatalysts for ethanol-fuelled vehicles
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Category: Emissions Control
Subject: Autocatalysts for ethanol-fuelled vehicles
Question
It has been claimed that E85-fuelled vehicles will produce a twenty-fold increase in acetaldehyde emissions per car. My question is, would an autocatalyst do anything to control these emissions?
Answer
E85 is a blend of 15% ethanol in gasoline, and is one of a number of options being considered for future fuels. Ethanol can be derived from a number of agricultural sources which take up CO2 from the atmosphere as they grow, and when used as fuel they contribute less to net atmospheric CO2 compared to gasoline.
Three-way catalysts provide a very efficient way of removing harmful emissions from gasoline vehicle exhausts, and are now fitted to all vehicles. They start to become effective within a few seconds after starting the engine, but in these few seconds trace amounts of emissions from the engine can reach the vehicle tailpipe.
The size of this “cold start” emission is carefully regulated and has been considerably reduced as emission control technology has developed.
Ethanol may be partially converted to aldehydes during the short cold start period, and these may pass through the catalyst for the few seconds it takes to reach catalyst operating temperature. Aldehydes have a much stronger odour than hydrocarbons formed from gasoline combustion. Emission control specialists are aware of this and are currently developing new technologies to reduce these very low emissions still further.
These new technologies work by trapping the aldehydes and other combustion products while the catalyst reaches operating temperature, and then releasing them after a short time to be removed by the catalyst in the normal way. The goal is to enable new lower carbon fuels to be used without any effect on the vehicle emissions.
Answer posted 09 May 2007
Submitted by: Ms Sara Coles
Affiliation: Platinum Metals Review
Answered by: Robert Brisley
Affiliation: Development Manager, Environmental Catalysts and Technologies, Johnson Matthey
